In engines of different types and particularly piston engines there are a number of places where a pin or shaft rotates relative to a member. That member or the pin or both may be subject to movement. In today's engine such relatively rotatable junctions are rarely designed to be immersed in the oil in the crank case. Instead, typically lubrication of joints on the crank shaft is accomplished by providing ducts through the crank shaft to individual bearing areas. An oil pump supplies oil to an oil gallery of ducts in the engine block connected to the crank shaft through the main bearings. The oil supplied to the bearings is under high pressure which causes the oil to spread out through the bearing and beyond onto the surface of the crank shaft. Oil on the crank shaft is flung off to lubricate other parts of the engine, particularly the cylinders and their pistons. Remote rotational joints like the wrist pin between the piston and its connecting rod receive a heavy splattering of oil on exposed surfaces. It is expected that some oil will work its way into the very limited space between a pin and the bore of a piston or a connecting rod. Thus in such remote locations, lubrication depends upon the relatively small amount of oil splashing from the crank shaft some distance up into the cylinders, for example.
A typical remote junction between a pin and a linkage member which is subject to some relative rotation is the wrist pin connection which connects the piston rod to the piston. In such a location there is essentially no pressure on the oil splashed into the area to urge the oil into the space between the bore and the pin. Nevertheless, some lubrication does occur at the wrist pin and any other locations which, like the wrist pin, are subject to receiving oil splash periodically. However, the amount of lubrication has never been totally satisfactory in such locations. The more power that is demanded from a given piston displacement, the more a better mode of lubrication is needed. Even relatively well lubricated junctions like the crank shaft could be better lubricated to great advantage.
Various means of supplementing lubrication from the exposed ends of the bore have been tried, for example, channels through the link member to the bore in various types of configurations. Unfortunately all such techniques have had limited success and a great need still exists for a more satisfactory means of lubricating in this splashed oil type of environment.